1. Field of the Invention
This invention generally relates to heaters used in automatic coffee makers. More specifically, this invention relates generally to the configuration of the base plate, heater element and water tube found in automatic coffee makers.
2. Description of the Related Art
Drip coffee makers typically include a base plate, a water tube and an electric heater element. The purpose of the heater is two-fold. The heater is used to boil water which flows into the water tube. The heated water expands and flows to the top of the coffee maker where it descends through the coffee grounds and into the coffee pot. The heater also warms the base plate which keeps the brewed coffee hot after it is brewed.
It is known in the art to die cast coffee maker base plates out of aluminum. A known configuration includes a cast channel projecting from the bottom surface of the base plate. An appropriately shaped water tube is press fit into the channel to a position adjacent to the bottom surface of the base plate. A heater element is then press fit into the channel below the water tube so that the water tube is between the heater and the base plate. In this configuration, the heater has direct contact with the water tube at a point along the length of their respective tubular circumferences. The heater has direct contact with the base plate along either side of its tubular circumference where the heater is adjacent to the base plate channel. A heater in this configuration heats water in the water tube by direct contact and indirectly via heating of the base plate.
Another existing design uses an aluminum extrusion where the water tube and heater channel are manufactured as a single part. The heater channel and water tube are extruded so that they share one longitudinal surface. The water tube is placed between the heater and the base plate. In this configuration, the heater heats the water tube directly and the base plate indirectly via the water tube.
These prior art designs share several problems. First, the aluminum castings or extrusions are relatively expensive to manufacture. Second, the aluminum materials have properties (such as a relatively low melting point) which limit the power of the heating element which can be used. Third, these designs produce a narrow contact interface between the heater and water tube. The small contact surface between the water tube and the heater does not permit the efficient transfer of heat from the heater to the water tube. Finally, many consumers claim that the aluminum materials adversely affect the taste of the coffee. Aluminum is reactive with acids found in coffee and may actually be dissolved into the heated water and ultimately the brewed coffee.